1. Field of the Invention
The present invention relates to alignment of an ophthalmologic apparatus for measuring optical characteristics of an eye to be examined.
2. Related Background Art
According to an eye refractive power measuring apparatus serving as an ophthalmologic apparatus, which is described in Japanese Patent Application Laid-Open No. 2002-186585, an alignment reference index is set by projecting an alignment index light flux to an eye to be examined. The alignment between the eye to be examined and the refractive power measuring apparatus is performed using the reference index by so-called auto alignment for electrically driving an eye examination optical portion of the refractive power measuring apparatus relative to the eye to be examined in the left/right, up/down, and forward/backward directions.
In the ophthalmologic apparatus for performing the measurement through such auto alignment, the measurement is always performed on the eye to be examined at the same location thereof. For example, assume that the eye to be examined has opacity resulting from cataract at the central region of the crystalline lens. In this case, even if measurement is tried multiple times, the measurement on the central region including the opacity is repeated by the auto alignment. Therefore, a measurement light flux is blocked by the opacity, so that the measurement light flux cannot be detected. As a result, there is a problem in that the measurement is not completed because a measurement error is repeated.
In addition to such an auto alignment function for performing the alignment measurement, the ophthalmologic apparatus has the same manual measurement function as that of a conventional eye examination apparatus. In the manual measurement function, an operator operates the eye examination optical portion in the left/right, up/down, and forward/backward directions to move the eye examination optical portion to a desirable position. The alignment measurement is performed at the position.
However, when the alignment measurement is manually performed, it is necessary for the operator to operate the eye examination optical portion taking into consideration not only left/right and up/down alignments but also forward/backward alignment (that is, focusing). Thus, the usability of the ophthalmologic apparatus having the auto alignment function impairs under the current circumstances.